Inorg. Chem. 1993, 32, 1066-1067
1066
Rafael Usbn,' Juan FomieS, Larry R. Falvello, Miguel A. Usbn, Isabel Usbn, and Santiago Herrero Departamento de Qufmica Inorglnica, Instituto de Ciencia de Materiales de Aragh, Universidad de Zaragoza-CSIC, E-50009Zaragoza, Spain Received November 6. I992 The chemistry of palladium in a formal oxidation state I is dominated1q2by binuclear compounds doubly bridged by bis(dipheny1phosphino)methane (dppm) or related ligands. Recently, Braunstein and co-workers have characterized3the tetranuclear {[Pd(p-Cl)(p-dppm)Pd](p-dppm)]dBF4)2, which contains two dipalladium(1) units. Here, wedescribe thesynthesis4of an octanuclear palladium(1) cluster containing four such moieties 2Pd2(dba),CHC1,
+ 4Pd(SC6Fs),dppm
-
ether
{ [P~(P-SCU~.~S) (P-dppm)Pdl (p-SC6FS) 1
14
1+
6dba
+ 2CHC1,
The I9F and 31PNMR data5 would be consistent with any formulation ([Pd(p-SC6Fs)(p-dppm)Pd]Oc-SC6F5)j, (nL 2), and indeed the highest observed peak in the mass spectrumS corresponds ton = 2. However, thestructureofcomplex 1, established by a single-crystal X-ray study: shows this compound to be octanuclear (n = 4, Figure 1). Taking into account the symmetry, the M S results, and preliminary reactivity studies, the compound can best be described as formed by four metal-metal bonded 'Pd(p-SC6Fs)(p-dppm)Pd"units [d(Pdl-Pd2)= 2.581(3) A] (Figure 2) which are bridged through four additional pentafluorobenzenethiolato groups to form a 12-membered puckered cycle, with the four dppm ligands sitting in turn above and below the ring, since the molecule lies on a crystallographic 4 axis; a further metal-metal
Figure 1. Molecular structure of compound 1.
( I ) (a) Russell, M. J. H.: Barnard, C. F. J. In Comprehensiue Coordination Chemistry: Wilkinson, G., Gillard, R. D., McCleverty, J. A,, Eds.; Pergamon PressLtd.: Oxford,England, 1987,Vol. 5.p 1103. (b) Balch, A. L. Comments Inorg. Chem. 1984, 3, 51. (2) Maitlis, P. M.; Espinet, P.; Russell, M. J. H. In Comprehensiue Organometallic Chemistry: Wilkinson, G.. Stone, F. G. A,, Abel, E. W., Eds.; Pergamon Press Ltd.: Oxford, England, 1982, Vol. 6, p 265. (3) Braunstein, P.; Luke, M. A.; Tiripicchio, A,; Tiripicchio-Camellini, M. Angew. Chem., Int. Ed. Engl. 1987, 26, 768. (4) A mixture of Pd2(dba)3.CHCl3 (0.2588 g. 0.25 mmol) and Pd(SC6Fs)2dppm (0.4445 g, 0.5 "01) in diethyl ether (120 mL) was stirred in the dark for 7 days at room temperature. The resulting dark burgundy solid was filtered off, washed with Et20 (10 X 2 mL), and dried in vacuo over P205. Yield: 63%. Anal. Calcd (found): C, 44.1 (44.6); H, 2.1 (2.2). IR (Nujol, Gin cm-I): S C ~ Fgroups J 1084 s, 976 vs; v ( C S ) 848 vs; dppm 1437 vs, 1098 s, 999 m, 748 m, 691 vs. ( 5 ) I9F NMR (188.2 MHz, reference CFC13, saturated CDCI, solution, 20 "C): ~ - 1 2 7 . 3 ( d , ~ F ) , - 1 2 9 . 7 ( d , ~ F ) , - 1 5 9 . 0 ( t , ~ F ) , - 1 6 4 . 7 ( t , ~ F ) , -165.5 (m, m-F), -165.8 (m, m-F). "P NMR (80.98 MHz, reference external 85% H~POI):6 -5.5 ppm. MS (FAB-, 3-nitrobenzylalcohol matrix): m/e 1990 (M+/2, I I%), 1699 (M+/2 - Pd - dppm + S C ~ F J , Figure 2. Numbering scheme for the asymmetric unit. Selected bond 11%). 1315 (M+/2 - Pd - 2dppm + SC6FJ. 6%), 1209 (M+/2 - 2Pd - 2dppm + SC6Fs. 5%), 917 (M+/2 - Pd - 2dppm - SC6Fs, 6%), 81 1 lengths (A) and bond angles (deg): PdI-PI = 2.235(7), Pd2-P2 = (M+/2 - 2Pd - 2dppm - SC6F5, IS%), 700 (M+/2 - 3Pd - 2dppm 2.267(7), P d l S 2 = 2.331(6), P d 2 S 2 = 2.328(6), P d l S l a = 2.412(6), SC6Fs, 39%), 671 (M+/2 - 3Pd - 2dppm - SC6Fs - s, loo%), 640 Pd2Sl 2.398(6); S2-Pdl-PI 148.9(2), S2-Pd2-PZ 153.0(2), (M+/2 - 3Pd - 2dppm - S C ~ F-J 2s. 40%), 506(M+/2 - 3Pd - 2dppm P d 2 S 1 - P d l a = 102.2(2), P 1 - P d l S l a = 101.4(2), Sl-PdZ-P2 = - ~ S C ~ F82%), S , 476 (M+/2 - 3Pd - 2dppm - ~ S C ~ -F SJ, 65%). 101.0(2). (6) Crystalssuitable forstructure investigation weregrown by slow diffusion of diethylether into a solution of 1 in chloroform at -28 OC. X-ray H ~ ~group . Z Id; O Ca ~=H I ~ ;interaction between palladium atoms in different binuclear units structure analysis: P ~ ~ P ~ S ~ F ~ C I ~ ~space 17.906(9) A, c = 24.736(6) A, V = 793 I(6) A3; Z = 2; size 0.38 x 0.30 can be excluded, since the closest distance is d(Pd1a-Pd2) = X0.30mm3;A(MoKa) =0.710 73A. T = 173K;absorptioncorrection ( I 1 *-scans with transmission factors 0.791 84.8798); Siemens-Stoe 3.743(3) A. Whereas the phosphorus and the S1 atoms show a AED2 four-circle diffractometer, e 2 8 scan method, 3' 5 28 5 51"; pseudotetrahedral environment, the S2 atom bridging the two total number of reflections 4057; 2190 unique reflections with F,, 2 palladium centers of the asymmetric unit deviates strongly from 5.0u(Fo):heavy atom method, refinement of F,,to R = 6.03%. R, = 7.02%. gof = 1.06; Pd, S, P. F. CI-C,, and C20425 anisotropic. this geometry, forming a PdIS2-Pd2 angle of 67.3O(2).
0020- 1669/93/' 1332- 1066$04.00/0
0 1993 American Chemical Society
Communications In each unit, the two heavy atoms linked by the metal-metal bond, the S2, and the phosphorus atoms of the diphosphine are almost coplanar (mean deviation 0.0695 A); the methylenic carbon deviates from this plane, resulting in an envelope conformation (dihedral angle 37.2'). The Pdl-PI and Pd2-P2 bonds are almost at right angles to the metal-metal bond (92.8(2) and 97.2(2)', respectively). The torsion angle S1-Pd2-PdlSla is -13.6', i. e., the central ring is puckered. A noteworthy feature is that the perfluorophenyl rings of the thiolato groups of each asymmetryc unit are parallel (dihedral angle 1.4O). and 3.20A apart; their rings are somewhat displaced, however. The rings are tilted, forming dihedral angles of 85.6 and 84.7O to the PdlPd2PlP2.52 plane; possibly weak residual
Inorganic Chemistry, Vol. 32, No. 7, 1993
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interactions between the Pdl and F37 (distance: 2.945(15) A) atoms and Pd2 and F31 atoms (distance: 3.048(14) A) are responsible for this geometry. The angles formed by any other contiguous pair of aryl rings are in the range 6-15O.
Acknowledgment. We are grateful to the Spanish Comisi6n Interministerial de Ciencia y Tecnologfa (CICYT) for financial support (Project PB91-0692) and for a FormaciQ de Personal Investigador grant to S.H. SuppkmentaryM.terialAv.iLbk Tables giving a summary of crystal structuredetermination data, atomic coordinates and equivalent isotropic displacement coefficients, bond lengths and angles, and anisotropicthermal parameters for compound 1 (8 pages). Ordering information is given on any current masthead page.
